The capx I'm adding contains two ways.One when the variable "A_SINGLE_OBJECT" is = 0 uses a single sprite that displays different frames when spawned.You can see the code for it in event 3.

If you change the value of this variable then the code from event 4 kicks in and then allows you to spawn several object types.For this example I used sprites, but as the "one frame" example shows, there is no need to have several sprite objects when you can use instances of a single one displaying several frames.